Method for separating physical layer functions in wireless communication system

ABSTRACT

The present disclosure relates to a communication method and a system thereof that fuses a 5G communication system, for supporting data transmission rates higher than 4G systems, with IoT technology. The present disclosure can be applied to intelligent services (e.g. smart homes, smart buildings, smart cities, smart cars or connected cars, health care, digital education, retail, or security and safety related services), on the basis of 5G communication technology and IoT related technology. The present disclosure relates to a method and a device for separating physical layer functions of a base station.

TECHNICAL FIELD

The disclosure relates to a wireless communication system. Inparticular, the disclosure relates to a method and apparatus for a splitbetween physical layer functions in a wireless communication system.

BACKGROUND ART

To meet the increased demand for wireless data traffic since thedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a “Beyond 4G Network” or a“Post LTE System”.

Implementation of the 5G communication system in higher frequency(mmWave) bands, e.g., 60 GHz bands, is being considered in order toaccomplish higher data rates. To decrease propagation loss of radiowaves and increase the transmission distance, beamforming, massivemultiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO),array antenna, analog beam forming, and large scale antenna techniquesare being discussed for the 5G communication system.

In addition, in the 5G communication system, there are developmentsunder way for system network improvement based on advanced small cells,cloud Radio Access Networks (RANs), ultra-dense networks,device-to-device (D2D) communication, wireless backhaul, moving network,cooperative communication, Coordinated Multi-Points (CoMP),reception-end interference cancellation, and the like.

In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and slidingwindow superposition coding (SWSC) as advanced coding modulation (ACM)and filter bank multi carrier (FBMC), non-orthogonal multiple access(NOMA), and sparse code multiple access (SCMA) as advanced accesstechnology have been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving into theInternet of Things (IoT) where distributed entities, such as things,exchange and process information without human intervention. TheInternet of Everything (IoE), which is a combination of IoT technologyand Big Data processing technology through connection with a cloudserver, has emerged. As technology elements, such as “sensingtechnology”, “wired/wireless communication and network infrastructure”,“service interface technology”, and “security technology” have beendemanded for IoT implementation, recently there has been research into asensor network, Machine-to-Machine (M2M) communication, Machine TypeCommunication (MTC), and so forth. Such an IoT environment may provideintelligent Internet technology services that create new values forhuman life by collecting and analyzing data generated among connectedthings. The IoT may be applied to a variety of fields including smarthome, smart building, smart city, smart car or connected car, smartgrid, health care, smart appliances, and advanced medical servicesthrough convergence and combination between existing InformationTechnology (IT) and various industrial applications.

In line with these developments, various attempts have been made toapply the 5G communication system to IoT networks. For example,technologies such as a sensor network, Machine Type Communication (MTC),and Machine-to-Machine (M2M) communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud RadioAccess Network (RAN) as the above-described Big Data processingtechnology may also be considered to be an example of convergencebetween the 5G technology and the IoT technology.

Meanwhile, as communication systems evolve, there is increasing growthin demand for splitting base station.

DISCLOSURE OF INVENTION Technical Problem

In legacy LTE systems, a radio interface protocol stack involves aphysical (PHY) layer, a medium access control (MAC) layer, a radio linkcontrol (RLC) layer, a packet data convergence protocol (PDCP) layer,and a radio resource control (RRC) layer. Among them, the PHY layer isresponsible for mapping transport channels onto physical channels. Indetail, the PHY layer is in charge of the procedure of generating andtransmitting a radio frequency signal through various operations such ascoding/decoding on information bits, modulation/demodulation, hybridautomatic request (HARQ) processing, and time-frequency resourcemapping.

However, the hierarchical protocol structure of the legacy LTE systemcannot handle efficiently a rapidly increasing number of antennas and agrowing channel bandwidth in line with the advance of communicationsystems, which necessitates an improvement method.

The technical goals to be achieved through the disclosure are notlimited to just solving the aforementioned problems, and otherunmentioned technical problems will become apparent from the disclosedembodiments to those of ordinary skill in the art.

Solution to Problem

According to a disclosed embodiment, a method for a first physical (PHY)entity to communicate with a second PHY entity in a wirelesscommunication system includes performing communication with the secondPHY entity by transmitting or receiving messages to or from the secondPHY entity via a fronthaul interface, wherein the first PHY entityperforms a lower physical layer processing operation of a base stationand the second PHY entity performs a higher physical layer processingoperation.

Preferably, the first PHY entity performs the lower physical layerprocessing operation and a radio frequency (RF) signal processingoperation, the lower physical layer processing operation including atleast one of Fast Fourier Transform (FFT), cyclic prefix (CP)addition/removal, precoding, beamforming, or physical random accesschannel (PRACH) filtering and the higher physical layer processingoperation including at least one of channel coding/decoding,modulation/demodulation, layer mapping, resource element (RE) mapping,channel estimation, or PRACH detection.

Preferably, the messages include user plane messages and control planemessages, the user plane messages including at least one of a downlinkin-phase/quadrature (IQ) message, an uplink IQ message, a soundingreference signal (SRS) message, or a physical random access channel(PRACH) message and the control plane messages including at least one ofa resource element (RE) bitmap message, a physical resource block (PRB)bitmap message, a scheduling information message, or a terminal channelinformation message.

Preferably, a type of the user plane message is indicated by a subtypefield value, and a type of the control plane message is indicated by acontrol type field value in a data field and the subtype field value.

According to a disclosed embodiment, a first physical (PHY) entitycommunicating with a second PHY entity in a wireless communicationsystem includes a transceiver configured to transmit and receive signalsand a controller configured to control to perform communication with thesecond PHY entity by transmitting or receiving messages to or from thesecond PHY entity via a fronthaul interface, wherein the first PHYentity performs a lower physical layer processing operation of a basestation, and the second PHY entity performs a higher physical layerprocessing operation.

According to a disclosed embodiment, a method for a second PHY entity tocommunicate with a first PHY entity in a wireless communication systemincludes performing communication with the first PHY entity bytransmitting or receiving messages to or from the first PHY entity via afronthaul interface, wherein the first PHY entity performs a lowerphysical layer processing operation of a base station and the second PHYentity performs a higher physical layer processing operation.

According to a disclosed embodiment, a second physical (PHY) entitycommunicating with a first PHY entity in a wireless communication systemincludes a transceiver configured to transmit and receive signals and acontroller configured to control to perform communication with the firstPHY entity by transmitting or receiving messages to or from the firstPHY entity via a fronthaul interface, wherein the first PHY entityperforms a lower physical layer processing operation of a base station,and the second PHY entity performs a higher physical layer processingoperation.

Advantageous Effects of Invention

The method proposed in the disclosure is advantageous in terms ofimproving communication efficiency and facilitating management of a basestation while reducing implementation complexity of the base station insuch a way of splitting functions of the base station.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a wireless network architectureaccording to a disclosed embodiment;

FIG. 2 is a block diagram illustrating a configuration of a base stationaccording to a disclosed embodiment;

FIG. 3 is a block diagram illustrating a configuration of a terminalaccording to a disclosed embodiment;

FIG. 4 is a diagram illustrating a physical layer of a base stationaccording to a disclosed embodiment;

FIG. 5 is a block diagram illustrating a configuration of a splitphysical layer according to a disclosed embodiment;

FIG. 6A is a block diagram illustrating a configuration of a splitphysical layer according to another disclosed embodiment;

FIG. 6B is a block diagram illustrating a configuration of a splitphysical layer according to another disclosed embodiment;

FIG. 7 is diagram illustrating split physical layer architectureaccording to a disclosed embodiment;

FIG. 8 is diagram illustrating split physical layer architectureaccording to another disclosed embodiment;

FIG. 9 is diagram illustrating split physical layer architectureaccording to another disclosed embodiment;

FIG. 10 is a diagram illustrating message flows between two PHY entitiesaccording to a disclosed embodiment;

FIG. 11 is a diagram illustrating a message structure according to adisclosed embodiment;

FIG. 12 is a diagram illustrating another message structure according toa disclosed embodiment;

FIG. 13 is a diagram illustrating another message structure according toa disclosed embodiment;

FIG. 14 is a diagram illustrating another message structure according toa disclosed embodiment;

FIG. 15 is a diagram illustrating another message structure according toa disclosed embodiment;

FIG. 16 is a diagram illustrating another message structure according toa disclosed embodiment;

FIG. 17 is a diagram illustrating another message structure according toa disclosed embodiment;

FIG. 18 is a diagram illustrating another message structure according toa disclosed embodiment;

FIG. 19 is a diagram illustrating another message structure according toa disclosed embodiment;

FIG. 20 is a message flow diagram illustrating physical layer messageflows according to a disclosed embodiment;

FIG. 21 is a message flow diagram illustrating physical layer messageflows according to another disclosed embodiment;

FIG. 22 is a message flow diagram illustrating physical layer messageflows according to another disclosed embodiment;

FIG. 23 is a message flow diagram illustrating physical layer messageflows according to another disclosed embodiment; and

FIG. 24 is a message flow diagram illustrating physical layer messageflows according to another disclosed embodiment.

MODE FOR THE INVENTION

Exemplary embodiments of the disclosure are described in detail withreference to the accompanying drawings. The same reference numbers areused throughout the drawings to refer to the same or like parts.Detailed descriptions of well-known functions and structuresincorporated herein may be omitted to avoid obscuring the subject matterof the disclosure.

Detailed descriptions of technical specifications well-known in the artand unrelated directly to the disclosure may be omitted to avoidobscuring the subject matter of the disclosure. This aims to omitunnecessary description so as to make the subject matter of thedisclosure clear.

For the same reason, some elements are exaggerated, omitted, orsimplified in the drawings and, in practice, the elements may have sizesand/or shapes different from those shown in the drawings. Throughout thedrawings, the same or equivalent parts are indicated by the samereference numbers.

Advantages and features of the disclosure and methods of accomplishingthe same may be understood more readily by reference to the followingdetailed descriptions of exemplary embodiments and the accompanyingdrawings. The disclosure may, however, be embodied in many differentforms and should not be construed as being limited to the exemplaryembodiments set forth herein; rather, these exemplary embodiments areprovided so that this disclosure will be thorough and complete and willfully convey the concept of the disclosure to those skilled in the art,and the disclosure will only be defined by the appended claims. Likereference numerals refer to like elements throughout the specification.

It will be understood that each block of the flowcharts and/or blockdiagrams, and combinations of blocks in the flowcharts and/or blockdiagrams, can be implemented by computer program instructions. Thesecomputer program instructions may be provided to a processor of ageneral-purpose computer, special purpose computer, or otherprogrammable data processing apparatus, such that the instructions thatare executed via the processor of the computer or other programmabledata processing apparatus create means for implementing thefunctions/acts specified in the flowcharts and/or block diagrams. Thesecomputer program instructions may also be stored in a non-transitorycomputer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the non-transitorycomputer-readable memory produce articles of manufacture embeddinginstruction means that implement the function/act specified in theflowcharts and/or block diagrams. The computer program instructions mayalso be loaded onto a computer or other programmable data processingapparatus to cause a series of operational steps to be performed on thecomputer or other programmable apparatus to produce a computerimplemented process such that the instructions that are executed on thecomputer or other programmable apparatus provide steps for implementingthe functions/acts specified in the flowcharts and/or block diagrams.

Furthermore, the respective block diagrams may illustrate parts ofmodules, segments, or codes including at least one or more executableinstructions for performing specific logic function(s). Moreover, itshould be noted that the functions of the blocks may be performed in adifferent order in several modifications. For example, two successiveblocks may be performed substantially at the same time, or they may beperformed in reverse order according to their functions.

According to various embodiments of the disclosure, the term “module”means, but is not limited to, a software or hardware component, such asa Field Programmable Gate Array (FPGA) or Application SpecificIntegrated Circuit (ASIC), which performs certain tasks. A module mayadvantageously be configured to reside on the addressable storage mediumand configured to be executed on one or more processors. Thus, a modulemay include, by way of example, components, such as software components,object-oriented software components, class components and taskcomponents, processes, functions, attributes, procedures, subroutines,segments of program code, drivers, firmware, microcode, circuitry, data,databases, data structures, tables, arrays, and variables. Thefunctionalities of the components and modules may be combined into fewercomponents and modules or further separated into more components andmodules. In addition, the components and modules may be implemented suchthat they execute one or more CPUs in a device or a secure multimediacard.

It may be advantageous to set forth definitions of certain words andphrases used through the disclosure. The term “couple” and itsderivatives refer to any direct or indirect communication between two ormore elements, whether or not those elements are in physical contactwith one another. The terms “transmit,” “receive,” and “communicate,” aswell as derivatives thereof, encompass both direct and indirectcommunication. The term “or” is inclusive, meaning and/or. The phrase“associated with,” as well as derivatives thereof, means to include, beincluded within, interconnect with, contain, be contained within,connect to or with, couple to or with, be communicable with, cooperatewith, interleave, juxtapose, be proximate to, be bound to or with, have,have a property of, have a relationship to or with, or the like. Thephrase “at least one of,” when used with a list of items, means thatdifferent combinations of one or more of the listed items may be used,and only one item in the list may be needed. For example, “at least oneof: A, B, and C” includes any of the following combinations: A, B, C, Aand B, A and C, B and C, and A and B and C.

Preferred embodiments are described hereinafter with reference to theaccompanying drawings.

FIG. 1 is a diagram illustrating a wireless network architectureaccording to a disclosed embodiment.

FIG. 1 shows an exemplary wireless network 100 according to a disclosedembodiment. Although the following description is made of the exemplarydeployment of the wireless network 100 as shown in FIG. 1, thedisclosure may be applicable to other network deployments.

In FIG. 1, the wireless network 100 includes base stations 101, 102, and103. The base station 101 communicates with the base stations 102 and103 via at least one network 130. The base stations 102 and 103 mayprovide a radio access service to terminals 111, 112, 113, 114, 115, and116 located within their coverages 120 and 125. In FIG. 1, the basestations 101, 102, and 103 may communicate with the terminals 111, 112,113, 114, 115, and 116 via various radio access technologies (RATs)including 5G new radio (NR), LTE, LTE-A, high speed packet access(HSPA), WiMAX, and Wi-Fi.

In the following description, the term “base station” may mean an entitysuch as a transmission point (TP), a transmission and reception point(TRP), an enhanced node B (eNB), a gNB, a macro-cell, a femto-cell, anda Wi-Fi access point (AP); the term “terminal” may mean an entity suchas user equipment (UE), a mobile station, a subscriber station, awireless transmission reception unit (WTRU), and a user device.

It is obvious that the deployment of the wireless network 100 can bechanged in various manners as described with reference to FIG. 1. Forexample, the wireless network 100 may include arbitrary numbers of basestations and terminals, and each base station may communicate with oneor more terminals to connect the terminals to the network 130.

FIG. 2 is a block diagram illustrating a configuration of a base stationaccording to a disclosed embodiment. Although the description is made ofthe exemplary configuration of the base station 102 as shown in FIG. 2,the base station may also be configured to include other components inaddition to the components depicted in FIG. 2 or exclude some of thecomponents depicted in FIG. 2. The components constituting the basestation 102 as shown in FIG. 2 may be integrated among each other oreach subdivided into separate smaller parts.

In the embodiment of FIG. 2, the base station 102 includes a pluralityof antennas 205 a to 205 n, a plurality of RF transceivers 210 a to 210n, a transmission (TX) processing circuit 215, and a reception (RX)processing circuit 220. The base station 102 may include acontroller/processor 225, a memory 230, and backhaul/network interface235.

The RF transceivers 210 a to 210 n receive an RF signal transmitted byanother device (e.g., terminal and another base station) by means of theantennas 205 a to 205 n. The RF transceivers 210 a to 210 n performdown-conversion on the RF signal to produce a baseband signal. Thedown-converted signal is send to the RX processing circuit 220, whichperforms filtering, decoding, and/or digitalization on the downlinksignal to produce a baseband signal. The RX processing circuit 220 sendsthe produced baseband signal to the controller/processor 225, whichperforms an additional process on the baseband signal.

The TX processing circuit 215 may receive analog or digital data fromthe controller/processor 215. The TX processing circuit 215 performsencoding, multiplexing, and/or digitalization on the baseband data toproduce a baseband signal. The RF transceivers 210 a to 210 n receivethe baseband signal processed by the TX processing circuit 215 andperform up-conversion on the baseband signal to generate an RF signal tobe transmitted via the antennas 205 a to 205 n.

The RF transceivers 210 a to 210 n may also be referred to, along withat least one of the TX processing circuit 215 and the RX processingcircuit 220, as a transceiver.

The controller/processor 225 may include one or more processors forcontrolling overall operations of the base station 102. For example, thecontroller/processor 225 may control the RF transceivers 210 a to 210 n,the RX processing circuit 220, and the TX processing circuit 215 toreceive a forward channel signal and transmit a reverse channel signal.The controller/processor 225 may include one or a combination of acircuit and a program for processing an uplink (UL) channel and/or adownlink (DL) channel For example, the controller/processor 225 may beconfigured to execute one or more instructions stored in the memory 230.

The controller/processor 225 may be connected to the backhaul/networkinterface 235. The backhaul/network interface 235 enables the basestation 102 to communicate with another device or system via a backhaullink or network. The backhaul/network interface 235 may support wirelineor wireless communication.

The memory 230 is connected with the controller/processor 225. Thememory 230 may store various types of information or data beingprocessed by the base station 102.

FIG. 3 is a block diagram illustrating a configuration of a terminalaccording to a disclosed embodiment. Although the description is made ofthe exemplary configuration of the terminal 116 as shown in FIG. 3, theterminal 116 may also be configured to include other components inaddition to the components depicted in FIG. 3 or exclude some of thecomponents depicted in FIG. 3. The components constituting the terminal11 b as shown in FIG. 3 may be integrated among each other or eachsubdivided into separated smaller parts.

In the embodiment of FIG. 3, the terminal 116 includes one or moreantennas 305 a to 305 n , one or more RF transceivers 310 a to 310 n, aTX processing circuit 315, and an RX processing circuit 325. Theterminal 116 also includes a microphone 320, a speaker 315, aninput/output interface (I/O IF) 345, a processor 340, a touchscreen 350,a display 355, and a memory 360, which stores an operating system (OS)361 and at least one application 362.

The RF transceivers 310 a to 310 n receive an RF signal transmitted by abase station of a network by means of the antennas 305 a to 305 n. TheRF transceivers 310 a to 310 n perform down-conversion on the RF signalto produce a baseband signal. The down-converted signal is sent to theRX processing circuit 325, which produces a baseband signal byperforming filtering, decoding, and/or digitalization on thedown-converted signal. The RX processing circuit 325 may send theprocessed baseband signal to the processor 340 that performs anadditional process on the baseband signal or to the speaker 330 thatoutputs a sound signal.

The TX processing circuit 325 may receive analog or digital data fromthe processor 340 or analog or sound data input via the microphone 320.The TX processing circuit 325 performs encoding, multiplexing, and/ordigitalization on the baseband data to produce a baseband signal. The RFtransceivers 310 a to 310 n receive the baseband signal from the TXprocessing circuit and perform up-conversion on the baseband signal toproduce an RF signal to be transmitted by the antennas 305 a to 305 n.

Two or more of the RF transceivers 310 a to 310 n, the TX processingcircuit 315, and the RX processing circuit 325 may be integrated into acomponent, which may be referred to as a transceiver.

The processor 340 may include one or more processors for controllingoverall operations of the terminal 116. For example, the processor 340may control the RF transceivers 310 a to 310 n, the RX processingcircuit 325, and the TX processing circuit 315 to receive a forwardchannel signal and transmit a reverse channel signal. The processor 340may include one or a combination of a circuit and a program forprocessing a UL channel and/or a DL channel. For example, the processor340 may be configured to execute one or more instructions stored in thememory 360.

The processor 340 may execute other processes and programs stored in thememory and write data in the memory 360 or read the data out from thememory 360. The processor 340 may execute the application 362 on the OS361. The processor 340 may be connected to the I/O IF 345 that allowsanother device to connect to the terminal 116. The I/O IF 345 providesthe processor 340 with a communication pathway to other devices.

The processor 340 is connected with the touchscreen 350 and the display355. A user may input data to the terminal 116 via the touchscreen 350.The display 355 may perform text processing or graphic processing oninformation and data processed in the terminal 116 to display theinformation and data in a visualized manner.

The memory 360 is connected with the processor 340. The memory 360 maystore various types of information and data processed in the terminal116.

FIG. 4 is a diagram illustrating a physical layer of a base stationaccording to a disclosed embodiment. The upper part of FIG. 4 shows aphysical layer procedure of the base station for transmitting a downlinksignal, and the lower part of FIG. 4 shows a physical layer procedure ofthe base station for processing a received uplink signal.

In FIG. 4, the physical layer of the base station includes an RF unit(RU) in charge of an RF function and a digital unit (DU) in charge ofother functions of the physical layer with the exception of the RFfunction.

In FIG. 4, the DU of the base station performs channel coding on datachannels, control channels, and a physical broadcast channel (PBCH) forDL signal transmission, generates a UE-specific demodulation referencesignal (DMRS), and performs layer mapping. The DU performs resourceelement (RE) mapping per layer, precoding & digital beamforming (BF),and inverse fast Fourier transform/cyclic prefix addition (IFFT/CPaddition), and the RU generates an RF signal based on a processingresult received from the DU and transmits the RF signal in downlink bymeans of an antenna.

In FIG. 4, the RU of the base station receives an uplink signal from aterminal, processes the received signal, and sends the processed signalto the DU. The DU performs FFT/CP removal, BF, RE de-mapping, channelestimation/equalization, inverse discrete Fourier transform (IDFT),demodulation, and decoding on the received signal to acquire the dataand control channels, or performs uplink channel estimation based on asounding reference signal (SRS) acquired from the FFT/CP removed data,or performs physical random access channel (PRACH) detection throughPRACH filtering and pre-filtering on the signal received from the RU.

With the evolvement of the 3GPP standard, a massive MIMO antennastructure is considered as a promising technology for NR communicationsystems operating in an ultra-high frequency band above 6 GHz to meetthe requirements of increased radio communication channel bandwidth. Inthis regard, on the basis of the above-described RU-DU configuration inthe physical layer of the base station, a fronthaul bandwidth betweenthe RU and DU increases abruptly. Services being provided in such a nextgeneration communication system are characterized by exponentiallyincreasing the amount and diversified types of information to beprocessed and requirements for communication responsiveness and highspeed signal processing. There is therefore a need of a new proposal onthe physical layer of the base station for efficient communication byreflecting characteristics of such a communication environment.

FIG. 5 is a block diagram illustrating a configuration of a splitphysical layer according to a disclosed embodiment. In the embodiment ofFIG. 5, the physical layer 500 of the base station is configured to havetwo separate entities through a functional split.

The various functions of the physical layer 400 that have been describedwith reference to FIG. 4 may be functionally split in various manners.The physical layer 400 may be configured to have a first PHY entity 510including at least one of the functions of the physical layer 500 and asecond PHY entity 520 including at least one of the remaining functions,and the first and second PHY entities are connected via a fronthaulinterface 530 formed therebetween.

As shown in FIG. 5, the first PHY entity 510 is connected with anantenna and responsible for RF functions and it may be referred to aslow PHY layer. The second PHY entity 520 is responsible for theremaining functions with the exception of the function of the first PHYentity 510 and it may be referred to as high PHY layer.

Descriptions are made hereinafter in detail of the configurations of thefirst and second PHY entities 510 and 520.

FIG. 6A is a block diagram illustrating a configuration of a splitphysical layer according to another disclosed embodiment, and FIG. 6B isa block diagram illustrating a configuration of a split physical layeraccording to another disclosed embodiment.

FIG. 6A shows a detailed configuration of the first PHY entity 510described with reference to FIG. 5. The first PHY entity in charge ofone or more functions including the RF function among the physical layerfunctions of the base station, which may also be referred to as amassive MIMO unit (MMU) 610, includes an RF processing block 614connected to an antenna 614 and performing RF processing, a PHY-Lprocessing block 616 for performing some functions (i.e., lower physicallayer functions) of the physical layer, and a fronthaul interface block618 for communication with a second PHY entity.

The operations being performed by the RF processing block 614 and thePHY-L processing block 616 have been already described with reference toFIGS. 2 and 4. For example, the RF processing block 614 performs RFfrontend operations such as power amplification, low noise amplification(LNA), ADC/DAC conversion, and uplink/downlink switching. For example,the first PHY entity 610 may perform FFT/IFFT, precoding, digitalbeamforming, and PRACH filtering by means of the PHY-L processing block616.

Meanwhile, the first PHY entity (or MMU) 610 communicates messages withthe second PHY entity (or LDU that is described later) by means of thefronthaul interface 618. The fronthaul interface block 618 may send thesecond PHY entity a signal produced by processing an RF signal in thefirst PHY entity 610 and process a signal from the second PHY entity andsend the processed signal to the RF processing block 614 in order forthe RF processing block 614 to produce an RF signal. For example, thefronthaul interface block 618 of the first PHY entity 610 may performpacketization/depacketization on the messages being exchanged with thesecond PHY entity 620 for communication via an Ethernet protocol.

FIG. 6B shows a detailed configuration of the second PHY entitydescribed with reference to FIG. 5. The second entity in charge of oneor more functions with the exception of the RF function among thephysical layer functions of the base station, which may also be referredto as a light digital unit (LDU) 620, includes a fronthaul interfaceblock 622 for communication with the first PHY entity (or MMU) and aPHY-H processing block 624 for performing some functions (i.e., higherphysical layer functions) of the physical layer. The operations beingperformed by the PHY-H processing block 624 have been already describedwith reference to FIGS. 2 and 4. For example, the second PHY entity 620may perform channel coding/decoding, modulation/demodulation, channelestimation/equalization, RE mapping/de-mapping, and layer mapping bymeans of the PHY-H processing block 624.

Meanwhile, the second PHY entity (or LDU) 620 communicates messages withthe first PHY entity (or MMU) by means of the fronthaul interface block622. The fronthaul interface block 622 may process a signal receivedfrom the first PHY entity 610 or send a signal to be transmitted to thefirst PHY entity 610. For example, the fronthaul interface block 622 ofthe second PHY entity 620 may perform packetization/depacketization onthe messages being exchanged with the first PHY entity 610 forcommunication via an Ethernet protocol.

As described with reference to FIGS. 6A and 6B, by splitting thephysical layer functions into the first PHY entity (or MMU) and thesecond PHY entity (or LDU), it is possible to reduce a burden of thefronthaul bandwidth between the first and second PHY entities incomparison with the RU-DU configuration described with reference to FIG.4. Furthermore, because the MMU is responsible for some physical layerfunctions, it may be possible to reduce a burden caused by frequentreplacement of the MMU as is necessary for compliance with the evolvingstandard, especially when it has been deployed on the rooftop of abuilding or a telephone pole.

As described with reference to FIGS. 6A and 6B, the first PHY entity(i.e., MMU) and the second PHY entity (i.e., LDU) may be established asphysically separate devices responsible for some physical layerfunctions of their own. That is, the first and second PHY entities maybe established as separate hardware devices communicating with eachother through a wireline or wireless link via a fronthaul interface. Itmay also be possible to establish first and second PHY entities that arelogically separated in a hardware device.

FIGS. 7, 8, and 9 are diagrams illustrating split physical layerarchitectures according to a disclosed embodiment. FIGS. 7 and 8 eachshow exemplary architectures of the split physical layer for downlinktransmission, and FIG. 9 shows an exemplary architecture of the splitphysical layer for uplink transmission.

FIG. 7 shows an exemplary split physical layer architecture for applyingthe split physical layer described with reference to FIGS. 6A and 6B toan LTE/LTE-A communication system. That is, the split physical layerarchitecture 700 of FIG. 7 shows the split physical layer implemented inan eNB as a base station of the LTE/LTE-A communication system. In FIG.7, the physical layer of the eNB may be split into a first PHY entity(or MMU) 710 and a second PHY entity (or LDU) 720, which are connectedto each other via a fronthaul 730. The fronthaul 730 may also bereferred to as xRAN fronthaul (FH).

FIG. 8 shows an exemplary split physical layer architecture for applyingthe split physical layer described with reference to FIGS. 6A and 6B toan NR communication system. That is, the split physical layerarchitecture 800 of FIG. 8 shows the split physical layer implemented ina gNB as a base station of the NR communication system. In FIG. 8, thephysical layer of the gNB may be split into a first PHY entity (or MMU)810 and a second PHY entity (or LDU) 820, which are connected to eachother via a fronthaul 830 similar to that in FIG. 7.

FIG. 9 shows detailed physical layer operations along with signalingbetween a first PHY entity (or MMU) 910 and a second PHY entity (or LDU)920 configured as described with reference to FIGS. 6A and 6B via afronthaul 930.

The first PHY entity responsible for some functions including the RFfunction among the physical layer functions and the second PHY entityresponsible for remaining physical layer functions have been describedabove. Although the description has been that the first and second PHYentities may be respectively referred to as MMU and LDU, other names canbe used to specify the entities. For example, in association with acentral unit-distributed unit (CU-DU) split in which all of the layersof the base station are split, the first and second PHY entities may bereferred to as distributed unit lower layer part (DU-L) and distributedunit higher layer part (DU-H), respectively. As another example, inassociation with the RU-DU split of physical layer functions, the firstand second PHY entities may be referred to as radio unit (RU) and lowerlayer split-central unit (LLS-CU), respectively. It is obvious that thefirst and second PHY entities can be called by other names

Hereinabove, the description has been made in detail of the split of thephysical layer functions of the base station. Descriptions are madehereinafter in detail of the messages being exchanged and signalingprocedure between the first and second PHY entities.

FIG. 10 is a diagram illustrating message flows between two PHY entitiesaccording to a disclosed embodiment. Messages being exchanged between afirst PHY entity (or MMU) 1010 and a second PHY entity (or LDU) 1020 maybe sorted into user plane messages and radio-specific control planemessages.

The user plane messages being communicated between the first and secondPHY entities 1010 and 1020 carry data to be transmitted to a terminal ordata received from the terminal. According to an embodiment, the userplane messages may include an in-phase/quadrature (IQ) message 1032, anuplink IQ message 1034, a sounding reference signal (SRS) message 1036,and a physical random access channel (PRACH) message 1038. According toan embodiment, the control plane messages may include an RE bitmapmessage 1040, a physical resource block (PRB) bitmap message 1042, ascheduling information message 1044, and a UE channel informationmessage 1046.

The aforementioned messages are described in detail hereinafter.

The user plane messages abide by a message format defined in the IEEEstandard 1914.3. The type of a user plane message is indicated by asubtype field value in a radio-over-Ethernet (ROE) header. Table 1 showssubtype field values and types of user plane messages.

TABLE 1 Subtype field Mapping Description 0000 0000b RoE Control subtype Control packet between the RoE control node and RoE controllednode. 0000 0001b Reserved Reserved 0000 0010b RoE Structure-agnosticData payload packet with RoE data sub type common frame header andstructure-agnostic payload. 0000 0011b RoE Structure-aware Data payloadpacket with RoE CPRI data sub type common frame header andstructure-aware CPRI data payload. 0000 0100b RoE Slow C&M CPRI C&Mpayload packet with sub type common RoE frame header and structure-awareCPRI Slow C&M payload. 0000 0101b Reserved Reserved for future subtypes. 0000 1111b 0001 0000b RoE Native time Time domain data payloadpacket domain data sub type with RoE common frame header. 0001 0001b RoENative frequency Frequency domain data payload domain data sub typepacket with RoE common frame header. 0001 0010b RoE Native PRACH PRACHIQ data payload with data sub type common frame header 0001 0011b SRSsubtype SRS IQ data payload 0001 0100b Reserved Reserved for future subtypes. 0001 0111b 0001 1000b Radio specific Radio specific controlinformation control subtype 0001 0101b Reserved Reserved for future subtypes. 1111 1011b 1111 1100b- Experimental Reserved for experimentaltypes. 1111 1111b

In Table 1, the subtype field values 00010001b, 00010010b, and 00010011bmay indicate the IQ, PRACH, and SRS messages, respectively.

The control plane messages also abide by a message format defined in theIEEE standard 1914.3. The type of a control plane message may beindicated by a combination of the subtype field value in the ROE headerand a radio-specific (RS) control header field value in an RS controlheader of the data. For example, in Table 1, the subtype field value00011000b may indicate a control plane message, and the subtype of thecontrol message may be indicated by an RS control type field value asshown in Table 2.

TABLE 2 RS control type field Mapping Description 0000 0000b RE bitmapInformation about beam weights per RE 0000 0001b PRB bitmap Informationfor indicating whether each RB is used for cell-specific beamforming orfor UE-specific beamforming 0000 0010b Scheduling Information forindicating which UE information is allocated to each RB 0000 0011b UEchannel UE channel information obtained from information SRS data 00000100b Reserved For future use 1111 1111b

Tables 1 and 2 are illustrative of exemplary embodiments of the tablesfor use in indicating the type of a message between the first and secondPHY entities. That is, the type of a message being exchanged between thefirst and second PHY entities may be indicated in a different manner, bya different field, or with a different value.

Hereinafter, detailed descriptions are made of the message structureswith reference to FIGS. 11 to 19.

FIG. 11 is a diagram illustrating a structure of a user plane messageaccording to a disclosed embodiment. In the message structure shown inFIG. 11, the subtype field 1120 in the ROE header may be set to a valueindicative of inclusion of a user plane message in the data field 1130of the message. The value of the subtype field 1120 may also indicatethe type of the user plane message.

In the embodiment of FIG. 11, the subtype field 1120 may be set to 17(00010001b in Table 1) indicative of inclusion of an IQ message 1142 inthe data field 1130, 18 (00010010b in Table 1) indicative of inclusionof a PRAC message 1144 in the data field 1130, or 19 (00010011b inTable 1) indicative of inclusion of an SRS message 1146) in the datafield 1130.

FIG. 12 is a diagram illustrating a structure of a control plane messageaccording to a disclosed embodiment. In the message structure shown inFIG. 12, the subtype field 1220 of the ROE header may be set to apredetermined value to indicate inclusion of a control plane message inthe data field 1230. The subtype field 1220 is set to a value (e.g.,00011000b in Table 1) indicative of the inclusion of a control planemessage, the RS control type field 1240 in the data field 1230 may beset to a value indicative of the type of data included in the payload1250.

For example, the RS control type field 1240 may be set to one of thevalues listed in Table 2 to indicate inclusion of an RE bitmap message1262, a PRB bitmap message 1264, a scheduling information message 1266,or a UE channel information message 1268 in the payload 1250.

FIG. 13 is a diagram illustrating a detailed format of an IQ message.The IQ message 1300 may be used to convey frequency domain IQ samples inuplink or downlink. The data field 1310 of the IQ message 1300 maycontain IQ values for the first subcarrier of the first RB to the12^(th) subcarrier of the N^(th) RB, the IQ values being packetized inorder; each IQ value may be represented by less than 30 bits. The numberof bits for representing an IQ value may be preconfigured between thefirst and second PHY entities during a cell setup phase.

FIG. 14 is a diagram illustrating a detailed format of a PRACH message.The PRACH message 1400 may be used to convey time domain (or frequencydomain) PRACH IQ samples in uplink. The data field 1410 of the PRACHmessage 1400 may contain IQ samples packetized in a time domain samplingorder; each IQ value may be represented by less than 20 bits. The numberof bits for representing an IQ value may be preconfigured between thefirst and second PHY entities during a cell setup phase.

FIG. 15 is a diagram illustrating a detailed format of an SRS message.The SRS message 1500 may be used to convey frequency domain SRS IQsamples in uplink. The data field 1510 of the SRS message 1500 maycontain IQ values for the first subcarrier of the first RB to the12^(th) subcarrier of the N^(th) RB, the IQ values being packetized inorder; each IQ value may be represented by less than 30 bits. The numberof bits for representing an IQ value may be preconfigured between thefirst and second PHY entities during a cell setup phase.

FIG. 16 is a diagram illustrating a detailed format of an RE bitmapmessage. The RE bitmap message 1600 may include weight indicesindicating types of beam weights to be applied to individual REs. Thepayload 1615 in the data field of the RE bitmap message 1600 may containweight indices for the first RE of the first symbol of the first RB tothe 12^(th) RE of the 14^(th) symbol of the Nth RB, the weight indicesbeing packetized in order; the RB size N may be preconfigured betweenthe first and second PHY entities during a cell setup phase.

FIG. 17 is a diagram illustrating a detailed format of a PRB bitmapmessage. The PRB bitmap message 1700 may include information indicatingwhether each RB is used for cell-specific beamforming or UE-specificbeamforming The payload 1715 in the data field 1710 of the PRB bitmapmessage 1700 may contain from cell-specific beamforming indicator forthe first RB to cell-specific beamforming indicator for the N^(th) RB,the cell-specific beamforming indicators being packetized in order. Acell-specific indicator has a length of 1 bit, which is set to 0 b toindicate UE-specific beamforming and 1 b to indicate cell-specificbeamforming The RB size N may be preconfigured between the first andsecond PHY entities during a cell setup phase.

FIG. 18 is a diagram illustrating a detailed format of a schedulinginformation message. The scheduling information message 1800 may includeinformation indicating a terminal to which each RB is allocated. Thepayload 1815 in the data field 1810 of the scheduling informationmessage 1800 starts by encapsulating an uplink/downlink indicator thatis set to 0 for downlink and 1 for uplink. The uplink/downlink indicatoris followed by UE IDs of the terminal to which the first RB is allocatedon the first layer to the terminal to which the N^(th) RB is allocatedon the L^(th) layer, UE IDs being arranged in order in the payload 1815.The RB size N may be preconfigured between the first and second PHYentities during a cell setup phase.

FIG. 19 is a diagram illustrating a detailed format of a UE channelinformation message. The UE channel information message 1900 may includechannel information of a specific terminal. The payload 1915 in the datafield 1910 of the UE channel information message 1900 encapsulates a UEID having a length of 12 bits indicative of a specific terminal, an RBlocation having a length of 10 bits indicative of an SRS RB location forthe specific terminal, and an RB size having a length of 10 bitsindicative of an SRS RB size for the specific terminal in order. The UEID, RB location, and RB size are followed by IQ values for the RBlocation for the first antenna to the RB size+RB location for the M^(th)antenna, IQ values being arranged in order in the payload 1915. Each IQvalue may be represented by less than 30 bits, and the number of bitsfor representing an IQ value and the number of antennas M may bepreconfigured between the first and second PHY entities during a cellsetup phase.

Hereinafter, descriptions are made of the procedures for communicatingthe messages formatted as shown in FIGS. 11 to 19 between the first andsecond PHY entities.

FIG. 20 is a message flow diagram illustrating physical layer messageflows in a PRACH transmission procedure according to a disclosedembodiment. FIG. 20 shows message flows between a terminal 2010 and abase station 2020 and among a first PHY entity (i.e., MMU) 2022, asecond PHY entity (i.e., LDU) 2024, and a CU 2026 constituting the basestation 2020. The CU 2026 may be an entity operating on at least onelayer excluding the physical layer in the base station, e.g., an entityoperating on at least one of MAC, RLC, PDCP, and RRC layers. In FIG. 20,the first and second entities 2022 and 2024 may each be responsible forat least some of physical layer functions of the base station 2020 andmay be established to be responsible for all of the physical layerfunctions. The first and second PHY entities 2022 and 2024 and the CU2026 may be connected to each other to be responsible for all layerfunctions of the base station 2020.

In FIG. 20, the terminal 2010 transmits, at operation 2030, a randomaccess preamble to the base station 2020 for initial access to the basestation 2020. The terminal 2010 may transmit the random access preambleto the base station 2020 through a PRACH selected according to apredetermined rule. The first PHY entity 2022 responsible for the RFfunction of the base station 2020 receives the random access preambletransmitted by the terminal 2010, and the PHY-L processing block 616described with reference to FIG. 6A performs PRACH filtering on a signaltransmitted by the terminal to extract the random access preamble. Next,the first PHY entity 2022 sends a PHRACH message to the second PHYentity 2024 at operation 2040. The PRACH message 2040 transmitted by thefirst PHY entity 2022 may have the format described with reference toFIG. 14.

The second PHY entity 2024 processes the received PRACH message 2040 todetermine whether to allow the initial access of the terminal 2010 atoperation 2050 and, if it is determined to allow the initial access ofthe terminal 2010, sends a random access response (RAR) message 2060 tothe first PHY entity 2022 at operation 2060. Next, the first PHY entity2022 may transmit an RAR to the terminal 2010 at operation 2070.

FIG. 21 is a message flow diagram illustrating physical layer messageflows in an SRS message transmission procedure according to a disclosedembodiment. FIG. 21 shows message flows between a terminal 2110 and abase station 2120 and among a first PHY entity (i.e., MMU) 2122, asecond PHY entity (i.e., LDU) 2124, and a CU 2126 constituting the basestation 2120. The CU 2126 may be an entity operating on at least onelayer excluding the physical layer in the base station, e.g., an entityoperating on at least one of MAC, RLC, PDCP, and RRC layers. In FIG. 21,the first and second entities 2122 and 2124 may each be responsible forat least some of physical layer functions of the base station 2120 andmay be established to be responsible for all of the physical layerfunctions. The first and second PHY entities 2122 and 2124 and the CU2126 may be connected to each other to be responsible for all layerfunctions of the base station 2120.

In FIG. 21, the terminal 2110 may transmit an SRS to the base station2120 at operation 2130 in order for the base station 2120 to estimate anuplink channel. The first PHY entity 2122 receives the SRS transmittedby the terminal 2110 and sends the received SRS to the second PHY entity2124 because the SRS is processed by the PHY-H processing block 624 ofthe second PHY entity 2124 as described with reference to FIG. 6B. Thatis, the first PHY entity 2122 sends the SRS message to the second PHYentity 2124 at operation 2140. The SRS message sent by the first PHYentity may have the format described with reference to FIG. 15.

The second PHY entity 2124 may process the message received at operation2140 to estimate the uplink channel at operation 2150 by means of thePHY-H processing block 624 of the second PHY entity 2124 as describedwith reference to FIG. 6B.

FIG. 22 is a message flow diagram illustrating physical layer messageflows for making a beamforming/precoding weight determination bytransmitting an RE bitmap message, a PRB bitmap message, a schedulinginformation message, and a UE channel information message according to adisclosed embodiment. FIG. 22 shows message flows between a terminal2210 and a base station 2220 and among a first PHY entity (i.e., MMU)2222, a second PHY entity (i.e., LDU) 2224, and a CU 2226 constitutingthe base station 2220. The CU 2226 may be an entity operating on atleast one layer excluding the physical layer in the base station, e.g.,an entity operating on at least one of MAC, RLC, PDCP, and RRC layers.In FIG. 21, the first and second entities 2222 and 2224 may each beresponsible for at least some of physical layer functions of the basestation 2220 and may be established to be responsible for all of thephysical layer functions. The first and second PHY entities 2222 and2224 and the CU 2226 may be connected to each other to be responsiblefor all layer functions of the of the base station 2220.

In FIG. 22, the second PHY entity 2224 may send the first PHY entity2222 an RE bitmap message at operation 2230, a PRB message at operation2240, a scheduling information message at operation 2250, and a UEchannel information message at operation 2260. The second PHY entity2224 may transmit the above messages to the first PHY entity alltogether or independently of each other at different time points asshown in FIG. 22. The second PHY entity 2224 may first send two or moremessages among the messages shown in FIG. 22 and proceed to sendremaining messages in such an exemplary way of sending the RE bitmapmessage 2230 and the PRB bitmap message 2240 to the first PHY entity2222 first and proceeding to send the scheduling information message2250 and the UE channel information message 2260 to the first PHY entity2222.

Meanwhile, the first PHY entity 2222 may determine, at operation 2270,beamforming/precoding weights for transmitting a signal to the terminalbased on at least one of the messages received from the second PHYentity 2224. The first PHY entity 2222 may determine thebeamforming/precoding weights based on some of the messages receivedfrom the second PHY entity 2224, referencing radio resources to beallocated and a terminal to which the radio resources are allocated thatare indicated in the scheduling information message. The first PHYentity 2222 may also take the channel information of the terminal intoconsideration for determining the beamforming/precoding weights.

In the embodiment of FIG. 22, the RE bitmap message, the PRB bitmapmessage, the scheduling information message, and the UE channelinformation message may have the formats that have been respectivelydescribed with reference to FIGS. 16 to 19.

FIG. 23 is a message flow diagram illustrating physical layer messageflows in a downlink IQ message transmission procedure according to adisclosed embodiment. FIG. 23 shows message flows between a terminal2310 and a base station 2320 and among a first PHY entity (i.e., MMU)2322, a second PHY entity (i.e., LDU) 2324, and a CU 2326 constitutingthe base station 2320. The CU 2326 may be an entity operating on atleast one layer excluding the physical layer in the base station, e.g.,an entity operating on at least one of MAC, RLC, PDCP, and RRC layers.In FIG. 23, the first and second entities 2322 and 2324 may each beresponsible for at least some of physical layer functions of the basestation 2320 and may be established to be responsible for all of thephysical layer functions. The first and second PHY entities 2322 and2324 and the CU 2326 may be connected to each other to be responsiblefor all layer functions of the of the base station 2320.

In FIG. 23, the CU 2326 may send downlink user data processed by ahigher layer to the second PHY entity 2324 at operation 2330 via aninterface established between the CU 2326 as an entity responsible forhigher layer functions and the second PHY entity 2324. The interface maybe referred to as F1 interface, by way of example, or mid-haul interfaceconsidering that the interface between the first and second PHY entitieshas been named fronthaul interface.

The second PHY entity 2324 may convert the received downlink user datato IQ data and send a downlink IQ message including the converted IQdata to the first PHY entity 2322 at operation 2340. The IQ messagebeing sent by the second PHY entity 2324 may have the format describedwith reference to FIG. 13, and the first PHY entity 2322 generates an RFsignal based on the received IQ data and transmits the RF signal to theterminal 2310 in downlink at operation 2350. Here, the first PHY entity2322 may generate the signal by applying a beamforming/precoding weightdetermined according to the procedure described with reference to FIG.22 and transmitting the generated signal.

FIG. 24 is a message flow diagram illustrating physical layer messageflows in an uplink IQ message transmission procedure according to adisclosed embodiment. FIG. 24 shows message flows between a terminal2410 and a base station 2420 and among a first PHY entity (i.e., MMU)2422, a second PHY entity (i.e., LDU) 2424, and a CU 2426 constitutingthe base station 2420. The CU 2426 may be an entity operating on atleast one layer excluding the physical layer in the base station, e.g.,an entity operating on at least one of MAC, RLC, PDCP, and RRC layers.In FIG. 24, the first and second entities 2422 and 2424 may each beresponsible for at least some of physical layer functions of the basestation 2420 and may be established to be responsible for all of thephysical layer functions. The first and second PHY entities 2422 and2424 and the CU 2426 may be connected to each other to be responsiblefor all layer functions of the base station 2420.

In FIG. 24, the terminal 2420 generates and transmits an uplink signalto the base station 2420 at operation 2430, and the first PHY entity2422 of the base station 2420 converts the received signal to IQ dataand sends the IQ data to the second PHY entity 2424. The first PHYentity 2422 may send the second PHY entity 2424 an uplink IQ messageincluding the IQ data at operation 2440, the uplink IQ message havingthe format described with reference to FIG. 13. The first PHY entity2422 may apply a beamforming/precoding weight determined according tothe procedure described with reference to FIG. 22 in the procedure ofconverting the signal received from the terminal 2410 to the IQ data.

The second PHY entity 2424 processes the received IQ data to send uplinkuser data to the CU 2426 at operation 2450 via an interface establishedbetween the CU 2426 as an entity responsible for higher layer functionsand the second PHY entity 2424. This interface may be referred to as F1interface, by way of example, or mid-haul interface considering that theinterface between the first and second PHY entities has been namedfronthaul interface.

Although the exemplary embodiments disclosed in the specification anddrawings have been described using specific terms, the specification anddrawings are to be regarded in an illustrative rather than a restrictivesense in order to help understand the disclosure. It is obvious to thoseskilled in the art that various modifications and changes can be madethereto without departing from the broader spirit and scope of thedisclosure.

1-15. (canceled)
 16. A method performed by a distributed unit (DU)performing at least one physical layer function of a base station in awireless communication system, the method comprising: establishing afronthaul interface with a radio unit (RU) performing other physicallayer function of the base station; and communicating with the RU byperforming a modulation, a layer mapping and a resource element (RE)mapping for a downlink signal.
 17. The method of claim 16, furthercomprising communicating with the RU by performing at least one of an REdemapping, an equalization, a channel estimation, a detection and ademodulation for an uplink signal, wherein the uplink signal comprisesat least one of a physical uplink shared channel (PUSCH) transmission, asounding reference signal (SRS) and a physical random access channel(PRACH).
 18. The method of claim 17, wherein at least one of aprecoding, a digital beamforming, an inverse Fast Fourier Transform(iFFT), a cyclic prefix (CP) addition for the downlink signal isperformed by the RU, and wherein at least one of an FFT, a CP removaland a digital beamforming for the uplink signal is performed by the RU.19. The method of claim 16, wherein the downlink signal comprises atleast one of a physical downlink shared channel (PDSCH) transmission anda user equipment (UE) specific demodulation reference signal (DMRS). 20.A method performed by a radio unit (RU) performing at least one physicallayer function of a base station in a wireless communication system, themethod comprising: establishing a fronthaul interface with a distributedunit (DU) performing other physical layer function of the base station;and communicating with the DU by performing a precoding, a digitalbeamforming, an inverse Fast Fourier Transform (iFFT), a cyclic prefix(CP) addition for a downlink signal.
 21. The method of claim 20, furthercomprising communicating with the DU by performing at least one of anFFT, a CP removal and a digital beamforming for an uplink signal,wherein the uplink signal comprises at least one of a physical uplinkshared channel (PUSCH) transmission, a sounding reference signal (SRS)and a physical random access channel (PRACH).
 22. The method of claim21, wherein at least one of a modulation, a layer mapping and a resourceelement (RE) mapping for the downlink signal is performed by the DU, andwherein at least one of an RE demapping, an equalization, a channelestimation, a detection and a modulation for the uplink signal isperformed by the DU.
 23. The method of claim 20, wherein the downlinksignal comprises at least one of a physical downlink shared channel(PDSCH) transmission and a user equipment (UE) specific demodulationreference signal (DMRS).
 24. A distributed unit (DU) performing at leastone physical layer function of a base station in a wirelesscommunication system, the DU comprising: a fronthaul interfaceconfigured to communicate with a radio unit (RU); and at least oneprocessor configured to: establish a fronthaul interface with a radiounit (RU) performing other physical layer function of the base station,and communicate with the RU by performing a modulation, a layer mappingand a resource element (RE) mapping for a downlink signal.
 25. The DU ofclaim 24, wherein the at least one processor is further configured tocommunicate with the RU by performing at least one of an RE demapping,an equalization, a channel estimation, a detection and a demodulationfor an uplink signal, and wherein the uplink signal comprises at leastone of a physical uplink shared channel (PUSCH) transmission, a soundingreference signal (SRS) and a physical random access channel (PRACH). 26.The DU of claim 25, wherein at least one of a precoding, a digitalbeamforming, an inverse Fast Fourier Transform (iFFT), a cyclic prefix(CP) addition for the downlink signal is performed by the RU, andwherein at least one of an FFT, a CP removal and a digital beamformingfor the uplink signal is performed by the RU.
 27. The DU of claim 24,wherein the downlink signal comprises at least one of a physicaldownlink shared channel (PDSCH) transmission and a user equipment (UE)specific demodulation reference signal (DMRS).
 28. A radio unit (RU)performing at least one physical layer function of a base station in awireless communication system, the RU comprising: a fronthaul interfaceconfigured to communicate with a distributed unit (DU); and at least oneprocessor configured to: establish a fronthaul interface with a DUperforming other physical layer function of the base station, andcommunicate with the DU by performing a precoding, a digitalbeamforming, an inverse Fast Fourier Transform (iFFT), a cyclic prefix(CP) addition for a downlink signal.
 29. The RU of claim 28, wherein theat least one processor is further configured to communicate with the DUby performing at least one of an FFT, a CP removal and a digitalbeamforming for an uplink signal, and wherein the uplink signalcomprises at least one of a physical uplink shared channel (PUSCH)transmission, a sounding reference signal (SRS) and a physical randomaccess channel (PRACH).
 30. The RU of claim 29, wherein at least one ofa modulation, a layer mapping and a resource element (RE) mapping forthe downlink signal is performed by the DU, and wherein at least one ofan RE demapping, an equalization, a channel estimation, a detection anda modulation for the uplink signal is performed by the DU.
 31. The RU ofclaim 28, wherein the downlink signal comprises at least one of aphysical downlink shared channel (PDSCH) transmission and a userequipment (UE) specific demodulation reference signal (DMRS).